How many elements will be there in the 4th period if each orbital can hold 3 electrons?

#1

In the fourth period of the periodic table, the subshells 4s,3d, and 4p are only filled. So number of orbitals available for filling = 1+5+3 = 9. So number of elements is 3*9 = 27, by considering the condition given in question (an orbital can hold 3 electrons).

Is this answer right. Because in my book answer is given as 48 by considering ymthe f subshell.

#2

I think the reason that its given so in your book, might be because, each period can now more number of atoms, as the subshells are now completed quickly.

#3

I think this is right because 4 th period contains 4 subshell 4s,4p,4d,4f. And each contains 1,3,5,7 orbitals respectively.
So total no of electrons will be
13+33+53+73 = 48
Hence the reason is right.